Optical information medium

ABSTRACT

The present invention provides an optical information medium in which the recording and/or reproducing beam incident side surface displays excellent anti-staining properties and lubricity, as well as superior scratch resistance and abrasion resistance. An optical information medium comprising a film element composed of one or more layers including at least a recording layer ( 4 ) or a reflective layer, on a supporting substrate ( 20 ), wherein at least one of the supporting substrate ( 20 )-side surface and the film element-side surface is formed of a hard coat layer ( 8 ) comprising a cured product of the hard coat agent composition comprising a fluorine-containing block copolymer (A) and an active energy ray-curable compound (B).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical information medium such as aread-only optical disk, an optical recording disk or a magneto-opticalrecording disk, and more specifically to an optical information mediumin which the recording and/or reproducing beam incident side surfacedisplays excellent anti-staining properties and lubricity, as well assuperior scratch resistance and abrasion resistance.

2. Disclosure of the Related Art

On the surfaces of optical disks such as read-only optical disks,optical recording disks and magneto-optical recording disks, the stainsfrom various stain materials and the adhesion of fingerprints are causedduring use. These stains and adhesion fingerprints are undesirable, andaccordingly, the surfaces of optical disks may be subjected to asuitable surface treatment to improve the anti-staining property, reducethe adhesion of fingerprints, and improve the ease with whichfingerprints can be removed. For example, a variety of different waterrepellent and oil repellent treatments are being investigated for thesurfaces of optical disks.

Furthermore, the formation of a transparent, scratch resistant hard coaton the recording and/or reproducing beam incident side surface of theoptical information medium is also standard practice for improving thescratch resistance of the medium surface. Formation of this hard coat isconducted by applying an active energy ray-polymerizable/curablecompound containing at least 2 polymerizable functional groups such as(meth)acryloyl groups within each molecule onto the surface of themedium, and then curing the applied film by irradiation with activeenergy rays such as ultraviolet rays. However, because this type of hardcoat only aims to improve the scratch resistance, little can be expectedin terms of an anti-staining effect relative to stain materials such asdust, airborne oil mist or fingerprints.

One example of a hard coat with an anti-staining property relative toorganic stains is disclosed in Japanese Laid-open Patent Publication No.10-110118 (1998), which proposes the blending of a non-crosslinkingfluorine-based surfactant with a hard coat agent. The non-crosslinkingfluorine based surfactant contains no polymerizable double bonds, andundergoes no crosslinking with the base resin of the hard coat agent.

Furthermore, Japanese Laid-open Patent Publication No. 11-293159 (1999)proposes the blending of a combination of a non-crosslinkingfluorine-based surfactant and a crosslinking fluorine-based surfactantwith a hard coat agent. Examples of the crosslinking fluorine-basedsurfactant include fluorinated alkyl (meth)acrylates such asperfluorooctylethyl (meth)acrylate, hexafluoropropyl (meth)acrylate andoctafluoropentyl (meth)acrylate. These crosslinking fluorine-basedsurfactants contain polymerizable double bonds, and undergo crosslinkingand fixation to the base resin of the hard coat agent.

Japanese Laid-open Patent Publication No. 11-213444 (1999) discloses theapplication of a fluorine-based polymer to the surface of a conventionaloptical disk substrate formed from a polycarbonate or the like.

Japanese Laid-open Patent Publication No. 2002-190136 discloses anoptical information medium in which metal chalcogenide fine particles ofsilica or the like are blended into the hard coat, thereby improving thescratch resistance of the hard coat, and in which a film of a silanecoupling agent comprising water repellent or oil repellent groups isprovided on the hard coat, thereby further improving the anti-stainingproperties of the optical information medium surface.

SUMMARY OF THE INVENTION

By making the coefficient of friction of the optical information mediumsurface low, an impact caused when a hard projection contacts thesurface can be slipped away; therefore, the generation of scratches canbe suppressed. For this reason, it is desired to decrease thecoefficient of friction of the surface of the hard coat to improve thescratch resistance of the surface. Recent developments have seen theappearance of Blu-ray discs, in which the spot size of focused laserbeam is reduced by increasing the numerical aperture (NA) of theobjective lens to focus the recording/reproducing laser beam toapproximately 0.85, and at the same time reducing the wavelength λ ofthe recording/reproducing laser beam to approximately 400 nm, and thesediscs have a recording capacity four times or more that of DVD.Increasing NA generally leads to a decreased distance between theobjective lens and the surface of the optical information medium (i.e.,working distance), which significantly increases the likelihood that thesurface of the optical information medium will come into contact withthe objective lens, or the support of the lens, during the rotation ofthe optical information medium (for example, for NA of approximately0.85, working distance is approximately 100 μm, a significant decreasefrom conventional optical systems). For this reason, it is desired toreduce the coefficient of friction of the hard coat surface whileincreasing the scratch resistance of the surface.

However, such conventional hard coat materials as described above suffernot only from a variety of physical problems such as poor durability ofthe anti-staining property or insufficient hardness, but also tend to beexpensive to produce.

Accordingly, an object of the present invention is to provide an opticalinformation medium in which the surface upon which the recording and/orreproducing beam is incident displays excellent anti-staining propertiesand lubricity, as well as superior scratch resistance and abrasionresistance.

The present inventors made eager investigation. As a result, the presentinventors have found out that by forming at least one surface of anoptical information medium, and preferably the surface upon which therecording and/or reproducing beam is incident, as a hard coat layerformed from a cured product of a hard coat agent composition comprisinga fluorine-containing block copolymer and an active energy ray-curablecompound, an optical information medium that achieves the above objectcould be obtained.

The present invention comprises the followings:

(1) An optical information medium comprising a film element composed ofone or more layers including at least a recording layer or a reflectivelayer, on a supporting substrate, wherein at least one of the supportingsubstrate-side surface and the film element-side surface is formed of ahard coat layer comprising a cured product of a hard coat agentcomposition comprising a fluorine-containing block copolymer (A) and anactive energy ray-curable compound (B).

(2) The optical information medium according to (1), wherein thefluorine-containing block copolymer (A) comprises a fluorine-containingsegment and a hydroxyl group-containing segment.

(3) The optical information medium according to (2), wherein thefluorine-containing block copolymer (A) is a copolymer in which anactive energy ray-reactive group has been introduced into the hydroxylgroup-containing segment.

(4) The optical information medium according to (2), wherein thefluorine-containing block copolymer (A) is a copolymer in which anactive energy ray-reactive group has been introduced into the hydroxylgroup-containing segment via a urethane linkage.

(5) The optical information medium according to (2), wherein thefluorine-containing block copolymer (A) is a copolymer in which, intothe hydroxyl group-containing segment, a monomer containing oneethylenic unsaturated double bond and one isocyanate group within eachmolecule has been introduced via a urethane linkage derived from thehydroxyl group and the isocyanate group.

(6) The optical information medium according to any of (1) to (5),wherein the hard coat agent composition comprises 0.1 part by weight ormore and 10 parts by weight or less of the fluorine-containing blockcopolymer (A) per 100 parts by weight of the nonvolatile content of thecomposition. This nonvolatile content includes not only thefluorine-containing block copolymer (A) and the curable compound (B),but also optional components such as inorganic fine particles (C), aphotopolymerization initiator, and a variety of other additives, asdescribed below.

(7) The optical information medium according to any of (1) to (6),wherein the hard coat agent composition further comprises inorganic fineparticles (C) with an average particle size of not more than 100 nm.

(8) The optical information medium according to (7), wherein theinorganic fine particles (C) are either fine particles of a metal (orsemi-metal) oxide, or fine particles of a metal (or semi-metal) sulfide.

(9) The optical information medium according to (8), wherein theinorganic fine particles (C) are fine particles of silica.

(10) The optical information medium according to either one of (8) and(9), wherein the inorganic fine particles (C) are modified on thesurface with a hydrolyzable silane compound containing an active energyray-reactive group.

(11) The optical information medium according to any of (7) to (10),wherein the hard coat agent composition comprises 5 parts by weight ormore and 500 parts by weight or less of the inorganic fine particles (C)per 100 parts by weight of the active energy ray-curable compound (B).

(12) The optical information medium according to (11), wherein eitherone of the supporting substrate-side surface or the film element-sidesurface upon which the light is incident is formed of the hard coatlayer.

(13) The optical information medium according to either one of (11) and(12), comprising an information recording layer on the supportingsubstrate, a light-transmitting layer on the information recordinglayer, and the hard coat layer on the light-transmitting layer.

In the present invention, the term “optical information medium” isintended to encompass read-only optical disks, optical recording disks,magneto-optical recording disks, and other media.

The present invention provides an optical information medium in whichthe recording and/or reproducing beam incident side surface displaysexcellent anti-staining properties and lubricity, as well as superiorscratch resistance and abrasion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing one example of thelayer structure of an optical disk of the present invention;

FIG. 2 is a schematic cross-sectional view showing one example of thelayer structure of an optical disk of the present invention;

FIG. 3 is a schematic cross-sectional view showing another example ofthe layer structure of an optical disk of the present invention; and

FIG. 4 is a schematic cross-sectional view showing yet another exampleof the layer structure of an optical disk of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As follows is a description of an optical information medium of thepresent invention (hereafter also referred to as an optical disk), aswell as a method for producing such an optical information medium, withreference to the drawings. In an optical disk of the present invention,at least one of the supporting substrate-side surface and the filmelement-side surface, and preferably the surface upon which therecording/reproducing beam is incident, is formed of a hard coat layercomprising a cured product of a hard coat agent composition comprising afluorine-containing block copolymer (A) and an active energy ray-curablecompound (B).

-   1. Optical Information Media in Which the Film Element-Side Surface    Acts as the Surface Upon Which the Recording/Reproducing Beam is    Incident:

First an optical information medium, in which the film element-sidesurface acts as the surface upon which the recording/reproducing beam isincident, will be described.

FIG. 1 is a schematic cross-sectional view showing one example of thelayer structure of an optical disk of the present invention. Thisoptical disk is a recording medium, and comprises a recording layer (4)that functions as an information recording layer on a supportingsubstrate (20) of comparatively high rigidity, a light-transmittinglayer (7) on the recording layer (4), and a light transmitting hard coatlayer (8) on the light-transmitting layer (7). The hard coat layer (8)acts as the surface upon which the recording/reproducing beam isincident, and the laser beam for recording or reproducing is incidentthrough the hard coat layer (8) and the light-transmitting layer (7),and onto the recording layer (4). The thickness of thelight-transmitting layer (7), including the hard coat layer (8), ispreferably within a range from 30 to 150 μm, and even more preferablyfrom 70 to 150 μm. An example of this type of optical disk is theBlu-ray Disc. The hardness of the hard coat layer (8) side is at leastgrade B in a pencil hardness test.

Although not shown in the drawings, the present invention also includesoptical disks with two or more recording layers, in which an additionalrecording layer is provided on the recording layer (4) with a spacerlayer disposed therebetween. In such cases, the light-transmitting layer(7) and the hard coat layer (8) are formed on the recording layerpositioned farthest from the supporting substrate (20).

The present invention can be applied to all different manner ofrecording layers. In other words, the invention can be applied tophase-change type recording media, pit formation type recording media,and magneto-optical recording media. Normally, a dielectric layer or areflective layer is provided on at least one side of the recording layerin order to protect the recording layer and provide an optical effect,but this layer has been omitted in FIG. 1. Furthermore, the presentinvention is not restricted to recordable type media such as that shownin the drawings, and can also be applied to read-only type media. Insuch cases, the pit sequence is formed as an integrated part of thesupporting substrate (20), and the reflective layer (a metal layer or adielectric multilayered film) that covers the pit sequence functions asthe information recording layer.

An optical information medium of the present invention that employs aphase-change type recording medium will be described below.

FIG. 2 is a schematic cross-sectional view showing one example of thelayer structure of an optical disk of the present invention. In FIG. 2,an optical disk has a supporting substrate (20) having information pits,pregrooves, and other fine scale concavities-convexities formed on onesurface thereof. On this surface, the optical disk has a reflectivelayer (3), a second dielectric layer (52), a phase-change recordingmaterial layer (4), and a first dielectric layer (51) formed in thisorder, and further has a light transmitting layer (7) on the firstdielectric layer (51), and a hard coat layer (8) on the lighttransmitting layer (7). In this example, an information recording layeris formed of the reflective layer (3), the second dielectric layer (52),the phase-change recording material layer (4), and the first dielectriclayer (51). A film element necessary for recording or reproducing isformed of the information recording layer and the light transmittinglayer (7). When using the optical disk, a laser beam for recording orreproducing is incident through the hard coat layer (8) and the lighttransmitting layer (7), namely the film element side.

The supporting substrate (20) has a thickness of 0.3 to 1.6 mm,preferably of 0.4 to 1.3 mm, and includes information pits, pregrooves,and other fine scale concavities-convexities formed on the surface onwhich the recording layer (4) is formed.

The supporting substrate (20) is not required to be opticallytransparent when the optical disk is used in such a manner that a laserbeam is incident through the film element side as described above.However, as transparent materials, various plastic materials includingpolycarbonate resins, acrylic resins such as polymethyl methacrylate(PMMA), and polyolefine resins and the like may be used. Alternatively,glass, ceramics or metals and the like may be also used. If a plasticmaterial is employed, the pattern of the concavity-convexity in thesurface will be often produced by injection molding, whereas the patternwill be formed by a photopolymer process (2P process) in the case of anymaterial other than plastics.

The reflective layer (3) is usually deposited by a sputtering process onthe supporting substrate (20). As a material for the reflective layer, ametallic element, semi-metallic element, semiconductor element or acompound thereof may be used singly or compositely. More specifically,the material may be selected from known materials for the reflectivelayers such as Au, Ag, Cu, Al, and Pd. The reflective layer ispreferably formed as a thin film with a thickness of 20 to 200 nm.

The second dielectric layer (52), the phase-change recording materiallayer (4), and the first dielectric layer (51) are deposited in thisorder by sputtering process on the reflective layer (3), or on thesupporting substrate (20) in the case that no reflective layer isprovided.

The phase-change recording material layer (4) is formed of a materialchanging reversibly by irradiation of laser beam between the crystallinestate and the amorphous state, and exhibiting different opticalproperties between these states. Examples of such material includeGe—Sb—Te, In—Sb—Te, Sn—Se—Te, Ge—Te—Sn, In—Se—Ti, and In—Sb—Te. Further,to any such matrial, a trace of at least one metal selected from Co, Pt,Pd, Au, Ag, Ir, Nb, Ta, V, W, Ti, Cr, Zr, Bi, In and the like may beadded. A trace of reductive gas such as nitrogen also may be added.There is no limitation to the thickness of the recording material layer(4), which is for example in a range of about 3 to 50 nm.

The second dielectric layers (52) and the first dielectric layer (51)are formed on the top and under surfaces of the recording material layer(4), respectively, so as to sandwich the same. The second dielectriclayers (52) and the first dielectric layer (51) have not only a functionof protecting the recording material layer (4) mechanically andchemically but also a function as an interference layer for adjustingthe optical properties. The second dielectric layers (52) and the firstdielectric layer (51) may each consist of either a single layer or aplurality of layers.

The second dielectric layers (52) and the first dielectric layer (51) ispreferably formed of an oxide, a nitride, a sulfide, or a fluoride or acomposite thereof, containing at least one metal selected from Si, Zn,Al, Ta, Ti, Co, Zr, Pb, Ag, Zn, Sn, Ca, Ce, V, Cu, Fe, and Mg. Further,the second dielectric layers (52) and the first dielectric layer (51)preferably have an extinction coefficient k of 0.1 or less.

There is no limitation to the thickness of the second dielectric layer(52), which is preferably for example in a range of about 20 to 150 nm.There is no limitation to the thickness of the first dielectric layer(51), either, which is preferably for example in a range of about 20 to200 nm. Setting the thicknesses of the second dielectric layers (52) andthe first dielectric layer (51) in these ranges makes it possible toadjust reflection.

The light transmitting layer (7) is formed on the first dielectric layer(51) by using active energy ray-curable material, or light-transmittingsheet such as a polycarbonate sheet.

The active energy ray-curable material for the light transmitting layer(7) should be optically transparent, exhibit low optical absorption orreflection in the laser wavelength range to be used, and have lowbirefringence, and is selected from ultraviolet ray-curable materialsand electron ray-curable materials on these conditions.

Specifically, the active energy ray-curable material is constitutedpreferably of the ultraviolet ray- (electron ray-) curable compound orits composition for polymerization. Examples include monomers,oligomers, polymers and the like in which groups to be crosslinked orpolymerized by irradiation with ultraviolet rays, such as acrylic typedouble bonds such as in ester compounds of acrylate and methacrylate,epoxy acrylates and urethane acrylates, allyl type double bonds such asin diallyl phthalate, and unsaturated double bonds such as in maleicacid derivatives and the like have been contained or introduced into amolecule. These are preferably polyfunctional, particularlytrifunctional or more, and may be used alone or in combination thereof.While monofunctional ones may be used for necessary.

The ultraviolet ray-curable monomer is preferably a compound with amolecular weight of less than 2000, and the oligomer is preferably acompound with a molecular weight of 2000 to 10000. These includestyrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycoldimethacrylate, diethylene glycol diacrylate, diethylene glycolmethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylateetc., and particularly preferable examples include pentaerythritoltetra(meth)acrylate, pentaerythritol tri(meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolpropanedi(meth)acrylate, (meth)acrylate of phenol ethylene oxide adduct, etc.Besides, the ultraviolet ray-curable oligomer includes oligoesteracrylate, acrylic modified urethane elastomer etc.

The ultraviolet ray- (electron ray-) curable material may contain knownphotopolymerization initiators. The photopolymerization initiator is notparticularly necessary when electron rays are used as the active energyrays. However, when ultraviolet rays are used, the initiator isnecessary. The photopolymerization initiator may be properly selectedfrom the usual photopolymerization initiators such as acetophenone,benzoin, benzophenone, thioxanthone. Examples of a radical photoinitiator, among the photopolymerization initiators, include DAROCURE1173, IRGACURE 651, IRGACURE 184, and IRGACURE 907 (all of which areproducts manufactured by Ciba Specialty Chemicals Inc.). The content bypercentage of the photopolymerization initiator is, for example, fromabout 0.5 to 5% by weight with respect to the ultraviolet ray- (electronray-) curable component.

As the ultraviolet ray-curable material, a composition containing epoxycompound and a photo-cation polymerization catalyst is also preferablyused. The epoxy compound is preferably alicyclic epoxy compound,particularly the compound having 2 or more epoxy groups in the molecule.The alicyclic epoxy compound is preferably one or more of the followingcompounds: 3,4-epoxycyclohexyl methyl-3,4-epoxycyclohexane carboxylate,bis-(3,4-epoxycyclohexylmethyl) adipate, bis-(3,4-epoxycyclohexyl)adipate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metha-dioxane, bis(2,3-epoxycyclopentyl) ether and vinylcyclohexene dioxide etc. Although the epoxy equivalent of alicyclicepoxy compound is not particularly limited, it is preferably 60 to 300,more preferably 100 to 200 for attaining excellent curable properties.

The photo-cation polymerization catalyst used may be any of known onesand is not particularly limited. For example, it is possible to use oneor more of the followings: metal fluoroborates and boron trifluoridecomplexes, bis(perfluoroalkyl sulfonyl) methane metal salts, aryldiazonium compounds, aromatic onium salts of the group 6A elements,aromatic onium salts of the group 5A elements, dicarbonyl chelate of thegroups 3A to 5A elements, thiopyrylium salts, the group 6A elementshaving MF6 anions (M is P, As or Sb), triaryl sulfonium complex salts,aromatic iodonium complex salts, aromatic sulfonium complex salts etc.,and it is particularly preferable to use one or more of the followings:polyaryl sulfonium complex salts, aromatic sulfonium salts or iodoniumsalts of halogen-containing complex ions, and aromatic onium salts ofthe group 3A elements, the group 5A elements and the group 6A elements.The content by percentage of the photo-cation polymerization catalystis, for example, from about 0.5 to 5% by weight of the ultravioletray-curable component.

The active energy ray-curable material used for the light transmittinglayer preferably has a viscosity of 1000 to 10000 cp (at 25° C.).

In the formation of the light-transmitting layer (7), the application ofthe active energy ray-curable material onto the surface of the firstdielectric layer (51) is preferably conducted using a spin coatingmethod. Following application, this curable material can then be curedby irradiation with ultraviolet rays. This ultraviolet-ray irradiationmay be divided into a plurality of irradiation doses. Furthermore, theoperation of applying the active energy ray-curable material may also beconducted using a plurality of application repetitions, withultraviolet-ray irradiation conducted after each individual applicationrepetition. By dividing the ultraviolet-ray irradiation operation into aplurality of irradiation doses, the resin is able to be cured in astepwise manner, thus enabling a reduction in the stress thataccumulates within the disk at any one time due to curing shrinkage,leading to a reduction in the overall stress accumulated within thedisk. As a result, even if the thickness of the light-transmitting layer(7) is considerably large, as in the case described above, a disk withexcellent mechanical characteristics can still be produced.

Alternatively, in the present invention, a light-transmitting layer canalso be formed using a light transmitting resin sheet. In such a case,an active energy ray-curable material is applied onto the surface of thefirst dielectric layer (51), in a similar manner to that described abovefor formation of a light-transmitting layer, thus forming an uncuredresin material layer. A light transmitting sheet is then placed on thisuncured resin material layer as the light-transmitting layer (7), and bysubsequently irradiating the structure with active energy rays such asultraviolet rays and curing the underlying resin material layer, thelight transmitting sheet is bonded to the structure and forms thelight-transmitting layer (7). The active energy ray-curable material ofthis resin material layer preferably has a viscosity of 3 to 500 cp (at25° C.). Application of the resin material layer is preferably conductedusing a spin coating method, and the thickness of the resin materiallayer, following curing, is typically within a range from 1 to 50 μm.

The light transmitting sheet can use, for example, a polycarbonate sheetwith any desired thickness within a range from 30 to 150 μm. Morespecifically, the formation of the light-transmitting layer (7) involvesplacing the polycarbonate sheet of the desired thickness on the uncuredresin material layer under vacuum conditions (0.1 atmospheres or lower),returning the structure to atmospheric pressure, and then conductingirradiation with ultraviolet rays to cure the resin material layer.

A hard coat agent composition comprising the fluorine-containing blockcopolymer (A) and the active energy ray-curable compound (B) is appliedonto the light-transmitting layer (7), and is then cured by irradiationwith active energy rays such as ultraviolet rays, electron rays orvisible rays, thereby forming the hard coat layer (8). A description ofeach of the components of the hard coat agent composition is providedbelow.

The active energy ray-curable compound (B) is different from thecomponent (A), is the primary curable component in the hard coat agentcomposition, and is the component responsible for forming the matrix ofthe hard coat layer obtained after curing. There are no particularrestrictions on the structure of the curable compound (B), provided itis a compound that contains at least one active energy ray-polymerizablegroup selected from the group consisting of (meth)acryloyl group, vinylgroup, and mercapto group. In order to ensure a satisfactory level ofhardness for the resulting hard coat, the active energy ray-curablecompound (B) preferably comprises a polyfunctional monomers or oligomercontaining at least two, and preferably three or more, polymerizablegroups within each molecule.

Among such active energy ray-curable compounds (B), examples of thecompound having (meth)acryloyl group include urethane acrylates, epoxyacrylates, and ester acrylates, and specific examples include1,6-hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate,ethylene oxide modified bisphenol A di(meth)acrylate, trimethylolpropanetri(meth)acrylate, pentaerythritol tetra(meth)acrylate,ditrimethylolpropane tetra(meth)acrylate, dipentaerythritolhexa(meth)acrylate, pentaerythritol tri(meth)acrylate, and3-(meth)acryloyloxyglycerin mono(meth)acrylate. However, the compoundhaving (meth)acryloyl group is not limited to these examples.

Examples of the compound having vinyl group include ethylene glycoldivinyl ether, pentaerythritol divinyl ether, 1,6-hexanediol divinylether, trimethylolpropane divinyl ether, ethylene oxide modifiedhydroquinone divinyl ether, ethylene oxide modified bisphenol A divinylether, pentaerythritol trivinyl ether, dipentaerythritol hexavinylether, and ditrimethylolpropane polyvinyl ether. However, the compoundhaving vinyl group is not limited to these examples.

Examples of the compound having mercapto group include

-   ethylene glycol bis(thioglycolate),-   ethylene glycol bis (3-mercaptopropionate),-   trimethylolpropane tris(thioglycolate),-   trimethylolpropane tris(3-mercaptopropionate),-   pentaerythritol tetrakis(mercaptoacetate),-   pentaerythritol tetrakis(thioglycolate),-   and pentaerythritol tetrakis(3-mercaptopropionate). However, the    compound having mercapto group is not limited to these examples.

As the active energy ray-curable compound (B) contained in the hard coatagent composition, either a single compound or a combination of two ormore compounds may be used.

The fluorine-containing block copolymer (A) is used for imparting waterrepellency and/or lubricity to the surface of the hard coat layer. Thefluorine-containing block copolymer (A) comprises a fluorine-containingsegment and a hydroxyl group-containing segment.

The fluorine-containing segment is formed either from afluorine-containing monomer represented by the general formula (1) shownbelow, or from a fluorine-containing monomer represented by the generalformula (1) and a radical polymerizable monomer containing no hydroxylgroups. This fluorine-containing segment imparts water repellency, oilrepellency, and/or lubricity to the surface of the hard coat layer.CH₂═CR¹COOR²Rf  (1)

In this formula, R¹ represents either a hydrogen atom or a methyl group,

R² represents —C_(p)H_(2p)—, —C(C_(p)H_(2p+1))H—, —CH₂C(C_(p)H_(2p+1))H—or —CH₂CH₂O—, and

Rf represents —C_(n)F_(2n+1), —(CF₂)_(n)H,—(CF₂)_(p)OC_(n)H_(2n)C_(i)F_(2i+1), —(CF₂)_(p)OC_(m)H_(2m)C_(i)F_(2i)H,—N(C_(p)H_(2p+1))COC_(n)F_(2n+1), or —N(C_(p)H_(2p+1))SO₂C_(n)F_(2n+1).Furthermore, p is an integer from 1 to 10, n is an integer from 1 to 16,m is an integer from 0 to 10, and i is an integer from 0 to 16.

Specific examples of fluorine-containing monomers represented by thegeneral formula (1) include: CF₃(CF₂)₇CH₂CH₂OCOCH═CH₂, CF₃CH₂OCOCH═CH₂,CF₃(CF₂)₄CH₂CH₂OCOC(CH₃)═CH₂, C₇F₁₅CON(C₂H₅)CH₂OCOC (CH₃)═CH₂,CF₃(CF₂)₇SO₂N(CH₃)CH₂CH₂OCOCH═CH₂, C₂F₁₅SO₂N(C₃H₇)CH₂CH₂OCOC(CH₃)═CH₂,(CF₃)₂CF (CF₂)₆(CH₂)₃OCOCH═CH₂, (CF₃)₂CF(CF₂)₁₀(CH₂)₃OCOC(CH₃)═CH₂,CF₃(CF₂)₄CH(CH₃)OCOC(CH₃)═CH₂, CF₃CH₂OCH₂CH₂OCOCH═CH₂,C₂F₅(CH₂CH₂O)₂CH₂OCOCH═CH₂, (CF₃)₂CFO(CH₂)₅OCOCH═CH₂,CF₃(CF₂)₄OCH₂CH₂OCOC(CH₃)═CH₂, C₂F₅CON(C₂H₅)CH₂OCOCH═CH₂, CF₃(CF₂)₂CON(CH₃)CH(CH₃)CH₂OCOCH═CH₂, H(CF₂)₆C(C₂H₅)OCOC(CH₃)═CH₂,H(CF₂)₈CH₂OCOCH═CH₂, H(CF₂)₄CH₂OCOCH═CH₂, H(CF₂)₆CH₂OCOC(CH₃)═CH₂,CF₃(CF₂)₇SO₂N(CH₃)CH₂CH₂OCOC(CH₃)═CH₂, CF₃(CF₂)₇SO₂N(CH₃)(CH₂)₀OCOCH═CH₂, C₂F₅SO₂N(C₂H₅)CH₂CH₂OCOC(CH₃)═CH₂,CF₃(CF₂)₇SO₂N(CH₃)(CH₂)₄OCOCH═CH₂, andC₂F₅SO₂N(C₂H₅)C(C₂H₅)HCH₂OCOCH═CH₂. These monomers can either be usedsingularly, or in a combination of two or more different monomers.

Specific examples of the aforementioned radical polymerizable monomercontaining no hydroxyl groups include methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl(meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate,methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate,N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and tetrahydrofurfuryl (meth) acrylate. These monomerscan also be used either singularly, or in a combination of two or moredifferent monomers.

On the other hand, the hydroxyl group-containing segment has the effectof improving the compatibility with the polymer of the active energyray-curable compound (B). The hydroxyl group-containing segment may beformed from a radical polymerizable monomer containing a hydroxyl group.Examples of radical polymerizable monomers containing a hydroxyl groupinclude 2-hydroxyethyl (meth)acrylate, ethylene glycolmono(meth)acrylate, 2-hydroxypropyl (meth)acrylate,2-hydroxy-3-methoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl(meth)acrylate, 2-hydroxy-3-(2-ethylhexyloxy)propyl (meth)acrylate, and2-hydroxy-3-phenyloxypropyl (meth)acrylate. These monomers can either beused singularly, or in a combination of two or more different monomers.

Synthesis of the fluorine-containing block copolymer (A) can beconducted using any of a variety of known methods, by conducting atypical two-step bulk polymerization, suspension polymerization,solution polymerization, or emulsion polymerization, using either apolymeric peroxide or a polyazo compound.

The weight ratio (f/h) between the fluorine-containing segment (f) andthe hydroxyl group-containing segment (h) in the fluorine-containingblock copolymer (A) is preferably within a range from 10/90 to 90/10,and even more preferably from 20/80 to 80/20. If the proportion of thefluorine-containing segment (f) exceeds 90% by weight, then thecompatibility of the hard coat deteriorates, and the effect ofentanglement of the active energy ray-curable compound (B) weakens,leading to poorer durability. In contrast if the proportion of thefluorine-containing segment (f) is less than 10% by weight, then thewater and oil repellency properties are unsatisfactory, and the effectsof the fluorine cannot be adequately manifested.

In addition, in order to improve the level of fixation within the hardcoat layer, the fluorine-containing block copolymer (A) is preferably acopolymer in which an active energy ray-reactive group has beenintroduced into the hydroxyl group-containing segment via a urethanelinkage. If such an active energy ray-reactive group is introduced, thenthe active energy ray irradiation conducted during curing of the hardcoat causes crosslinking reactions between molecules of thefluorine-containing block copolymer (A), and between thefluorine-containing block copolymer (A) and the active energyray-curable compound (B), thus improving the fixation of the compound(A) within the hard coat layer. As a result, a medium is obtained thatdisplays extremely superior anti-staining properties and lubricity overa wide range of storage conditions and usage conditions. Examples of theactive energy ray-reactive group include (meth) acryloyl group and vinylgroup.

In the fluorine-containing block copolymer (A), a monomer containing oneethylenic unsaturated double bond and one isocyanate group within eachmolecule is preferably reacted with the hydroxyl group-containingsegment to introduce an ethylenic unsaturated double bond via a urethanelinkage derived from the hydroxyl group and the isocyanate group. Afluorine-containing block copolymer (A) containing an active energyray-reactive double bond that has been introduced in this manner is ableto suppress any increase in viscosity of the liquid of the hard coatagent composition.

Examples of this monomer include isocyanatoethyl (meth)acrylate andmethacryloyl isocyanate.

In terms of the effects of the fixation within the hard coat layer andothers, the molecular weight of the fluorine-containing block copolymer(A) is preferably within a range from about 5,000 to 100,000. Atmolecular weights of less than 5,000, a satisfactory fixation effect isdifficult to achieve in those cases where the copolymer contains noactive energy ray-reactive double bonds. If the molecular weight exceeds100,000, then the solubility of the copolymer in the hard coat liquiddeteriorates, and migration of the copolymer to the surface of the layerfollowing application becomes less efficient.

Specific examples of the fluorine-containing block copolymer (A) includeMODIPER-F220, F600, F2020, and F3035 (manufactured by NOF Corporation),and copolymers in which (meth)acryloyl groups or vinyl groups have beenintroduced into these commercially available copolymers are preferred,as well as copolymers in which (meth) acryloyl groups have beenintroduced via urethane linkages.

The fluorine-containing block copolymer (A) contained in the hard coatagent composition may be either a single copolymer or a combination oftwo or more different copolymers.

The hard coat agent composition preferably comprises 0.1 part by weightor more and 10 parts by weight or less, and even more preferably 0.5part by weight or more and 5 parts by weight or less, of thefluorine-containing block copolymer (A) per 100 parts by weight of thenonvolatile content of the composition. If the quantity of thefluorine-containing block copolymer (A) is more than 10 parts by weight,then although the lubricity improves, the hardness of the hard coatlayer tends to decrease, whereas in contrast, if the quantity is lessthan 0.1 part by weight, the lubricity improvement effect is minimal.The term “nonvolatile content” refers to those components that remain inthe hard coat layer following curing, and includes not only thefluorine-containing block copolymer (A) and the curable compound (B),but also optional components such as the inorganic fine particles (C)described below, photopolymerization initiators, and a variety of otheradditives.

In addition, the hard coat agent composition preferably also comprisesinorganic fine particles (C) with an average particle size of not morethan 100 nm. In order to ensure good transparency of the hard coatlayer, the average particle size of these inorganic fine particles (C)is typically not more than 100 nm, and preferably not more than 20 nm,and from the viewpoint of the restrictions associated with producing acolloid solution, is preferably at least 5 nm.

The inorganic fine particles (C) may, for example, be fine particles ofmetal (or semi-metal) oxides, or fine particles of metal (or asemi-metal) sulfides. Examples of the metals or semi-metals for theinorganic fine particles include Si, Ti, Al, Zn, Zr, In, Sn, and Sb.Aside from the oxides and sulfides, the inorganic fine particles (C) mayinclude selenides, tellurides, nitrides, and carbides. Examples of theinorganic fine particles include fine particles of silica, alumina,zirconia, and titania. Of these, silica fine particles are preferred.When added to the hard coat agent composition, such inorganic fineparticles enhance the abrasion resistance of the hard coat layer.

The silica fine particles are preferably surface-modified with ahydrolyzable silane compound containing active energy ray-reactivegroups. Such reactive silica fine particles undergo a crosslinkingreaction when exposed to active energy rays during curing of the hardcoat and are fixed in the polymer matrix. One example of such reactivesilica fine particles is the one described in Japanese Laid-Open PatentPublication No. 9-100111(1997), which is suitable for use in the presentinvention.

In those cases where inorganic fine particles (C) are used, the hardcoat agent composition preferably comprises 5 parts by weight or moreand 500 parts by weight or less of the inorganic fine particles (C), andeven more preferably 20 parts by weight or more and 200 parts by weightor less of the inorganic fine particles (C), per 100 parts by weight ofthe active energy ray-curable compound (B). If more than 500 parts byweight of the inorganic fine particles (C) is added, then the filmstrength of the hard coat layer tends to weaken, whereas if the quantityis less than 5 parts by weight, the level of improvement in the abrasionresistance of the hard coat layer achieved by adding the inorganic fineparticles (C) is minimal.

The hard coat agent composition may also comprise knownphotopolymerization initiators. The photopolymerization initiator is notparticularly necessary when electron rays are used as the active energyrays. However, when ultraviolet rays are used, the initiator isnecessary. The photopolymerization initiator may be properly selectedfrom the usual photopolymerization initiators such as acetophenone,benzoin, benzophenone, thioxanthone. Examples of a radical photoinitiator, among the photopolymerization initiators, include DAROCURE1173, IRGACURE 651, IRGACURE 184, and IRGACURE 907 (all of which areproducts manufactured by Ciba Specialty Chemicals Inc.). The content bypercentage of the photopolymerization initiator added to the hard coatagent composition is, for example, from about 0.5 to 5% by weight withrespect to the total amount of the aforementioned components (A), (B),and (C).

Furthermore, if required, the hard coat agent composition may alsocomprise other additives such as a non-polymerizable diluent, an organicfiller, a polymerization inhibitor, an antioxidant, an ultraviolet rayabsorber, a photo-stabilizer, an antifoamer, and a leveling agent.

In the present invention, the hard coat agent composition is appliedonto the light-transmitting layer (7), thus forming an uncured hard coatlayer, and this uncured layer is then irradiated with active energyrays, thereby curing the uncured layer and forming the hard coat layer(8).

The coating method for the application is not limited, and may be anyone of various coating methods such as spin coating, dip coating andgravure coating methods. In an alternate method in which alight-transmitting sheet is used to serve as the light-transmittinglayer (7), the hard coat layer (8) is first formed onto an elongate rawlight-transmitting sheet as described above, and disks are subsequentlystamped out from the raw sheet. In the same manner as described above,the disks are placed on the uncured resin material layer and the uncuredresin material layer is cured.

When the hard coat agent composition contains the non-reactive organicdiluent, the hard coat agent composition is first applied to form anuncured hard coat layer, which is then dried by heating to remove thenon-reactive organic solvent. Subsequently, the active energy rays areirradiated to cure the uncured layer and to thereby form the hard coatlayer (8). By first applying the hard coat agent composition using theorganic diluent and then removing the organic solvent by heating anddrying, the fluorine-containing block copolymer (A) tends to concentratein the proximity of the surface of the uncured hard coat layer. Theresult is more fluorine-containing block copolymer existing in theproximity of the surface of the cured hard coat layer (8). This furtherenhances the lubricity. The heating/drying process is preferably carriedout at a temperature of for example 40° C. or more and 100° C. or lessand over a time period of for example 30 seconds or more and 8 minutesor less, preferably 1 minute or more and 5 minutes or less, and morepreferably 3 minutes or more and 5 minutes or less. Examples of thenon-reactive organic diluent include, but are not limited to,propyleneglycol monomethylether acetate, propyleneglycolmonomethylether, ethyleneglycol monomethylether butylacetate, methylethyl ketone, methyl isobutyl ketone, and isopropyl alcohol. The activeenergy rays may be properly selected from ultraviolet rays, electronrays, visible rays, and other proper active energy rays. Preferably,ultraviolet rays or electron rays are used. The thickness of the hardcoat (8) after curing is adjusted to about 0.5 to 5 μm.

In this manner, a phase-change type optical recording disk such as thatshown in FIG. 2 may be produced, which represents an example of anoptical information medium in which the film element-side surface actsas the surface upon which the recording/reproducing beam is incident.

-   2. Optical Information Media in Which the Supporting Substrate-Side    Surface Acts as the Surface Upon Which the Recording/Reproducing    Beam is Incident:

Next an optical information medium, in which the supportingsubstrate-side surface acts as the surface upon which therecording/reproducing beam is incident, will be described.

FIG. 3 is a schematic cross-sectional view showing another example ofthe layer structure of an optical disk of the present invention. Theoptical disk shown in FIG. 3 comprises an information recording layer(4) on one surface of a light transmitting supporting substrate (20),and a protective layer (6) on the information recording layer (4),whereas a light transmitting hard coat layer (8) is formed on the othersurface of the supporting substrate (20). The hard coat layer (8) actsas the surface upon which the recording/reproducing beam is incident,and the laser beam for recording or reproducing is incident through thehard coat layer (8) and the supporting substrate (20), and onto therecording layer (4).

FIG. 4 is a schematic cross-sectional view showing yet another exampleof the layer structure of an optical disk of the present invention. Theoptical recording disk shown in FIG. 4 comprises an organic dye layer(4) on one surface of a light transmitting supporting substrate (20), areflective layer (3) on the dye layer (4), and another supportingsubstrate (21) that is bonded to the reflective layer (3) via aprotective and adhesive layer (61), whereas a light transmitting hardcoat layer (8) is formed on the other surface of the supportingsubstrate (20) The hard coat layer (8) acts as the surface upon whichthe recording/reproducing beam is incident. In this example, the dyelayer (4) and the reflective layer (3) make up the information recordinglayer. An example of this type of optical disk is the write-once DVD-Rformat.

In addition to the write-once DVD-R disk shown in FIG. 4, a variety ofother disk formats, including read-only DVD-ROM, and rewritable formatssuch as DVD-RAM and DVD-RW and the like can be commercially available.Read-only DVD formats include DVD-video and DVD-ROM, and with thesetypes of optical disks, concavities-convexities known as pits, which areused to record the information signals, are formed in the surface of thelight transmitting supporting substrate during production of thesubstrate, and a metal reflective layer such as Al, and then aprotective layer, are formed sequentially on the supporting substrate. Aseparate supporting substrate is then bonded to the protective layer viaan adhesive layer, thus completing the optical disk. In the case ofrewritable DVD formats, the information recording layer may be formed inthe same manner as for the phase-change type recording medium describedabove in the section 1.

The supporting substrate (20) uses a light transmitting base material.Conventionally, the light transmitting supporting substrate (20) isformed by injection molding of a polycarbonate resin, with informationformed in the surface of the resin as a series of prepits or pregrooves.However, other materials may also be used, and resins such as polyolefinresins can also be favorably employed. Alternatively, the supportingsubstrate can also be formed from a flat glass plate, by using the 2Pmethod to form a series of prepits or pregrooves.

A solution of an organic dye dissolved in a solvent is applied onto thesurface of the supporting substrate (20) using spin coating, and is thendried to form an organic dye layer (4) of the desired thickness. Theorganic dye can be selected from amongst the various cyanine dyes, azodyes, and phthalocyanine dyes or the like. Techniques other than spincoating, such as spray methods, screen printing methods or vacuumdeposition methods can also be used for forming the dye layer, and thethickness of the layer formed can be suitably adjusted in accordancewith the dye used.

In those cases where spin coating is used, the dye component isdissolved in a solvent and used in the form of an organic dye solution.The solvent should be a solvent that is capable of satisfactorilydissolving the dye, without having any deleterious effects on the lighttransmitting base material. The concentration of the dye solution ispreferably within a range from 0.01 to 10% by weight.

Specific examples of suitable solvents include alcohol based solventssuch as methanol, ethanol, isopropyl alcohol, octafluoropentanol, allylalcohol, methyl cellosolve, ethyl cellosolve, and tetrafluoropropanol;aliphatic or alicyclic hydrocarbon based solvents such as hexane,heptane, octane, decane, cyclohexane, methylcyclohexane,ethylcyclohexane, and dimethylcyclohexane; aromatic hydrocarbon basedsolvents such as toluene, xylene, and benzene; halogenated hydrocarbonbased solvents such as carbon tetrachloride, chloroform,tetrachloroethane, and dibromoethane; ether based solvents such asdiethyl ether, dibutyl ether, diisopropyl ether, and dioxane; ketonebased solvents such as 3-hydroxy-3-methyl-2-butanone; ester basedsolvents such as ethyl acetate and methyl lactate; and water, and ofthese, a solvent that does not attack the substrate base material shouldbe used. These solvents can either be used singularly, or incombinations of two or more different solvents.

There are no particular restrictions on the thickness of the organic dyelayer, although values from about 10 to 300 nm are preferred, and valuesfrom about 60 to 250 nm are particularly desirable.

A reflective layer (3) is provided on the organic dye layer (4). Thematerial for the reflective layer must be a material with asatisfactorily high reflectance at the wavelength of the reproducingbeam, and suitable examples include metal elements such as Au, Ag, Cu,Al, Ni, Pd, Cr, and Pt, as well as alloys of these metals. Furthermore,the elements listed below may also be included. Namely, metals andsemi-metals such as Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir,Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi.

The reflective layer can be formed using a sputtering method, ionplating method, chemical deposition method, or vacuum deposition method,although this is not a restrictive list. Furthermore, a conventionalinorganic or organic intermediate layer or adhesive layer may beprovided between the substrate base material and the reflective layer inorder to improve the reflectance and/or improve the recordingcharacteristics of the disk. There are no particular restrictions on thethickness of the reflective layer, although values from about 10 to 300nm are preferred, and values from about 80 to 200 nm are particularlydesirable.

Another supporting substrate (21) is usually bonded to the reflectivelayer (3) via a protective and adhesive layer (61). This supportingsubstrate (21) can use the same material as that used for the supportingsubstrate (20). There are no particular restrictions on the materialused for the adhesive layer (61), provided it is capable of bonding thetwo substrates (21) and (20) together, and protects the reflective layerfrom external forces, and conventional organic or inorganic materialscan be used. Examples of suitable organic materials includethermoplastic resins, thermosetting resins, and ultraviolet ray-curableresins. Furthermore, examples of suitable inorganic materials includeSiO₂, SiN₄, MgF₂, and SnO₂. Adhesive layers of thermoplastic resins orthermosetting resins can be formed by dissolving the resin in anappropriate solvent, applying the resin in solution form, and thendrying the applied solution. Ultraviolet ray-curable resins can eitherbe applied as is, or dissolved in an appropriate solvent to prepare thesolution for application, and then applied the solution, and the appliedfilm is then irradiated with ultraviolet rays to cure the resin andgenerate the layer. Examples of suitable ultraviolet ray-curable resinsinclude acrylate resins such as urethane acrylate, epoxy acrylate, andpolyester acrylate. These materials can be used singularly, or incombinations of two or more materials, and can be formed as either asingle layer, or a multilayered film.

Formation of the protective and adhesive layer (61) is conducted usingeither a application method such as the spin coating method used informing the recording layer or a casting method, or a different methodsuch as sputtering or chemical deposition.

Furthermore, the adhesive used in the bonding step can use any of avariety of different adhesives, including hot melt adhesives,ultraviolet ray-curable adhesives, heat curable adhesives, and tackytype adhesives, and is applied using a method that is appropriate forthe type of adhesive, such as roll coating, screen printing or spincoating, although in the case of DVD-R disks, on the basis of factorssuch as workability, productivity, and the resulting diskcharacteristics, an ultraviolet ray-curable adhesive is preferablyapplied using either a screen printing or spin coating method.

A light transmitting hard coat layer (8) is formed on the other surfaceof the supporting substrate (20). The material for the hard coat layer(8), and the method used for forming the layer are as described above inthe section 1. The hard coat layer (8) acts as the surface upon whichthe recording/reproducing beam is incident. The recording/reproducingbeam uses a laser beam with a wavelength of 650 or 660 nm. A blue laserbeam can also be used.

In the manner described above, a DVD-R disk such as that shown in FIG. 4may be produced, which represents an example of an optical informationmedium in which the supporting substrate-side surface acts as thesurface upon which the recording/reproducing beam is incident.

EXAMPLES

The present invention will now be described in detail with reference toexamples, which are not intended to limit the scope of the invention inany way.

Synthesis Example for a Fluorine-Containing Block Copolymer 1

A round bottom flask equipped with a stirrer was charged with 20 partsby weight of a fluorine-containing acrylic block copolymer (brand name:MODIPER-F600, manufactured by NOF Corporation), and 80 parts by weightof propyleneglycol-1-monomethylether-2-acetate, and the mixture wasstirred gently.

Once the fluorine-containing acrylic block copolymer had dissolved, 4.6parts by weight of 2-isocyanatoethyl methacrylate, 0.003 part by weightof hydroquinone, and 0.004 part by weight of tin octanoate were added,and the temperature was raised to 75° C. with constant stirring. Thereaction was allowed to proceed for 6 hours, and the reaction mixturewas then cooled to room temperature, yielding a solution (copolymer 1)comprising a solid content of 23% by weight.

The thus obtained solution was applied onto a release paper and driedunder reduced pressure to form a film, and when this film was analyzedusing infrared spectroscopic analysis, the peak derived from O—Hstretching vibration that had been observed at 3520 cm⁻¹ in thefluorine-containing acrylic block copolymer prior to reaction haddisappeared, whereas the peak derived from N—H stretching vibration hadappeared at 3390 cm⁻¹. Furthermore, a peak derived from the adjacentdouble bond stretching vibration of an NCO group was not observed at2270 cm⁻¹.

When a small quantity of an organic peroxide such as benzoyl peroxidewas added to the obtained solution, and the solution was then heated to70° C., the entire solution was converted to a gel-like solid. From theabove findings it was evident that the hydroxyl group of thefluorine-containing acrylic block copolymer and the isocyanate group ofthe 2-isocyanatoethyl methacrylate had reacted together to form aurethane linkage, thus introducing methacrylate group, which is capableof crosslinking via a radical polymerization, into a side chain of thefluorine-containing acrylic block copolymer.

Example 1

An optical recording disk sample with the layer structure shown in FIG.2 was produced as follows.

Using a disk shaped supporting substrate (20) (formed frompolycarbonate, diameter 120 mm, thickness 1.1 mm) in which informationrecording grooves had been formed, sputtering was used to form areflective layer (3) of thickness 100 nm comprising Al₉₈Pd₁Cu₁ (atomicratio) on the groove-side surface of the substrate. The depth of thegrooves, which is represented by light-path length at a wavelength λ=405nm, was set into λ/6. The recording track pitch in the groove-recordingscheme was set into 0.32 μm.

Subsequently, sputtering with an Al₂O₃ target was used to form a seconddielectric layer (52) of thickness 20 nm on the surface of thereflective layer (3). Sputtering using an alloy target comprising aphase-changing material was then used to form a recording layer (4) ofthickness 12 nm on the surface of the second dielectric layer (52). Thecomposition (atomic ratio) of the recording layer (4) wasSb₇₄Te₈(Ge₇In₁). Sputtering with a ZnS (80 mol %)-SiO₂ (20 mol %) targetwas then used to form a first dielectric layer (51) of thickness 130 nmon the surface of the recording layer (4).

Subsequently, a radical polymerizable, ultraviolet ray-curable materialwith the composition shown below was applied onto the surface of thefirst dielectric layer (51) by spin coating, and was then irradiatedwith ultraviolet rays under conditions including a use of high pressuremercury lamp (160 W/cm) in an air atmosphere, a separation between thelamp and the applied layer of 11 cm, and a total energy of 3 J/cm², thusforming a light transmitting layer (7) with a cured thickness of 98 μm.

(Light Transmitting Layer: Composition of the Ultraviolet Ray-CurableMaterial)

Urethane acrylate oligomer 50 parts by weight (DIABEAM UK6035,manufactured by Mitsubishi Rayon Co., Ltd.) Isocyanuric acid EO modifiedtriacrylate 10 parts by weight (ARONIX M315, manufactured by ToagoseiCo., Ltd.) Isocyanuric acid EO modified diacrylate  5 parts by weight(ARONIX M215, manufactured by Toagosei Co., Ltd.) Tetrahydrofurfurylacrylate 25 parts by weight Photopolymerization initiator  3 parts byweight (1-hydroxycyclohexyl phenyl ketone)

Subsequently, an ultraviolet ray-curable/electron ray-curable hard coatagent with the composition shown below was applied onto the lighttransmitting layer (7) by spin coating to form a coating, and theapplied coating was then heated at 60° C. for 3 minutes in an atmosphereto remove the diluent in the coating, and then irradiated with electronrays under nitrogen flow, thus curing the hard coat layer (8). Theelectron ray irradiation was conducted using a Min-EB electron raysirradiating device (manufactured by Toyo Ink Manufacturing Co., Ltd.),under conditions including an electron ray accelerating voltage of 50 kVand an irradiation dose of 100 kGy. The oxygen concentration of theirradiation atmosphere was 80 ppm. The thickness of the hard coat layer(8) after curing was 2 μm.

(Composition of the Hard Coat Agent)

Reactive group modified colloidal silica 100 parts by weight (dispersionmedium: propyleneglycolmonomethylether acetate, nonvolatile content: 40%by weight) Dipentaerythritol hexaacrylate  48 parts by weightTetrahydrofurfuryl acrylate  12 parts by weight Propyleneglycolmonomethylether acetate  40 parts by weight (unreactive diluent) Thefluorine-containing block copolymer 1  13 parts by weight

In this manner, a disk sample was prepared.

Example 2

In the formation of the hard coat layer (8), with the exceptions ofadding 3 parts by weight of 1-hydroxycyclohexyl phenyl ketone as aphotopolymerization initiator to the hard coat agent, and conducting thecuring process by irradiation with ultraviolet rays, under theconditions described below, instead of by irradiation with electronrays, a disk sample was prepared in the same manner as the example 1.

Type: high pressure mercury lamp (160 W/cm), total energy: 3 J/cm²,separation between the lamp and the applied layer: 11

Example 3

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with 3 parts by weight of MODIPER-F600 (manufactured by NOFCorporation, nonvolatile content: 100%), a disk sample was prepared inthe same manner as the example 2.

Comparative Example 1

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with 0.5 parts by weight of a fluorine based non-crosslinkingsurfactant FLUORAD FC-4430 (manufactured by Sumitomo 3M Ltd.), a disksample was prepared in the same manner as the example 2.

Comparative Example 2

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with 3 parts by weight of a fluorine based crosslinkingsurfactant M-1820 (from Daikin Chemicals Sales Corporation), a disksample was prepared in the same manner as the example 2.

Comparative Example 3

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with a mixture of 0.5 parts by weight of the fluorine basednon-crosslinking surfactant FLUORAD FC-4430 (manufactured by Sumitomo 3MLtd.) and 2 parts by weight of a fluorine based crosslinking surfactantViscoat 8F (manufactured by Osaka Organic Chemical Industry Ltd.), adisk sample was prepared in the same manner as the example 2.

Comparative Example 4

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with 10 parts by weight of the fluorine basednon-crosslinking surfactant FLUORAD FC-4430 (manufactured by Sumitomo 3MLtd.), a disk sample was prepared in the same manner as the example 2.

Comparative Example 5

With the exception of replacing the 13 parts by weight of thefluorine-containing block copolymer 1 in the composition of the hardcoat agent with 10 parts by weight of the fluorine based crosslinkingsurfactant M-1820 (from Daikin Chemicals Sales Corporation), a disksample was prepared in the same manner as the example 2.

Evaluations of the Disk Samples

Each of the disk samples prepared in the examples 1 to 3 and thecomparative examples 1 to 5 was subjected to the performance testsdescribed below.

(Evaluation of the Anti-Staining Property and the Durability of thatProperty)

The contact angle was measured for the hard coat surface of each disksample. Pure water was used as the measuring liquid, and the staticcontact angle was measured using a Face Contact-Angle meter manufacturedby Kyowa Interface Science Co., Ltd. The measurements were conductedunder conditions including a temperature of 20° C. and a relativehumidity of 60%. First, the initial contact angle (a) was measured.

Subsequently, in order to evaluate the durability of the anti-stainingproperty, the contact angle (b) after storage at high temperature, thecontact angle (c) after wiping with a solvent, and the contact angle (d)after wiping with a solvent following storage at high temperature werealso measured.

In the case of the contact angle (b) after storage at high temperature,each disk sample was stored at 80° C. (under dry conditions) for 500hours, and the contact angle was then remeasured under the sameconditions as those described above.

In the case of the contact angle (c) after wiping with a solvent,anon-woven cloth (Bemcot Lint-Free CT-8, manufactured by Asahi KaseiCo., Ltd.) was impregnated with acetone, and was then pressed againstthe hard coat surface of each disk sample with a load of 1000 g/cm², andwas reciprocated 100 times to be slid on the hard coat surface, beforethe contact angle was remeasured under the same conditions as thosedescribed above.

In the case of the contact angle (d) after wiping with a solventfollowing storage at high temperature, each disk sample was stored at80° C. (under dry conditions) for 100 hours, and was then subjected tosolvent wiping with acetone under the same conditions as those describedabove, before the contact angle was remeasured under the same conditionsas those described above.

Those disk samples that became charged as a result of the frictionbetween the disk sample surface and the non-woven cloth during theacetone wiping were thoroughly discharged prior to the contact anglemeasurements.

(Evaluation of Hardness)

The pencil hardness of the hard coat surface of each disk sample wasmeasured in accordance with JIS K5400.

The results from the above measurements are shown in Table 1.

From Table 1 it is evident that each of the disk samples of the examples1 to 3 displayed excellent anti-staining properties and durability ofthose properties, while maintaining favorable hardness of the hard coatsurface. Particularly, the disk sample of the example 2 displayedexcellent surface durability even after exposure to severe test such asthe acetone wiping. In addition, the disk sample of the example 1displayed excellent surface durability even after exposure to even moresevere test such as acetone wiping following high temperature storage.

The disk samples of the comparative examples 1 to 5 all showed poorinitial anti-staining properties, and as a result, the durability tests(b), (c), and (d) were not conducted. In the comparative examples 4 and5, because a large quantity of fluorine based surfactant was used, thehardness of the hard coat surface decreased.

In the above examples, a hard coat layer was provided on a phase-changetype optical disk. However, the present invention is not restricted touse with optical disks in which the recording layer is a phase-changetype layer, and can also be applied to read-only optical disks andwrite-once optical disks. Accordingly, the above examples representnothing more than sample illustrations of the invention, and must not beconsidered limiting in any way. In addition, any modifications whichfall within the scope of the appended claims are all considered part ofthe present invention.

TABLE 1 Contact Angle (degrees) After high After solvent wipingtemperature After solvent following high Pencil Disk Initial (a) storage(b) wiping (c) temperature storage (d) hardness Example 1 101  100 98 95H Example 2 101  102 90 60 H Example 3 100  106 61 60 H Comparative 65 —— — H example 1 Comparative 63 — — — H example 2 Comparative 65 — — — Hexample 3 Comparative 89 — — — B example 4 Comparative 89 — — — Bexample 5

1. An optical information medium comprising a film element composed ofone or more layers including at least a recording layer or a reflectivelayer, on a supporting substrate, wherein at least one of the supportingsubstrate-side surface and the film element-side surface is formed of ahard coat layer comprising a cured product of a hard coat agentcomposition comprising a fluorine-containing block copolymer (A) and anactive energy ray-curable compound (B).
 2. The optical informationmedium according to claim 1, wherein the fluorine-containing blockcopolymer (A) comprises a fluorine-containing segment and a hydroxylgroup-containing segment.
 3. The optical information medium according toclaim 2, wherein the fluorine-containing block copolymer (A) is acopolymer in which an active energy ray-reactive group has beenintroduced into the hydroxyl group-containing segment.
 4. The opticalinformation medium according to claim 2, wherein the fluorine-containingblock copolymer (A) is a copolymer in which an active energyray-reactive group has been introduced into the hydroxylgroup-containing segment via a urethane linkage.
 5. The opticalinformation medium according to claim 2, wherein the fluorine-containingblock copolymer (A) is a copolymer in which, into the hydroxylgroup-containing segment, a monomer containing one ethylenic unsaturateddouble bond and one isocyanate group within each molecule has beenintroduced via a urethane linkage derived from the hydroxyl group andthe isocyanate group.
 6. The optical information medium according toclaim 1, wherein the hard coat agent composition comprises 0.1 part byweight or more and 10 parts by weight or less of the fluorine-containingblock copolymer (A) per 100 parts by weight of the nonvolatile contentof the composition.
 7. The optical information medium according to claim1, wherein the hard coat agent composition further comprises inorganicfine particles (C) with an average particle size of not more than 100nm.
 8. The optical information medium according to claim 7, wherein theinorganic fine particles (C) are either fine particles of a metal (orsemi-metal) oxide, or fine particles of a metal (or semi-metal) sulfide.9. The optical information medium according to claim 8, wherein theinorganic fine particles (C) are fine particles of silica.
 10. Theoptical information medium according to claim 8, wherein the inorganicfine particles (C) are modified on the surface with a hydrolyzablesilane compound containing an active energy ray-reactive group.
 11. Theoptical information medium according to claim 7, wherein the hard coatagent composition comprises 5 parts by weight or more and 500 parts byweight or less of the inorganic fine particles (C) per 100 parts byweight of the active energy ray-curable compound (B).
 12. The opticalinformation medium according to claim 11, wherein either one of thesupporting substrate-side surface or the film element-side surface uponwhich the light is incident is formed of the hard coat layer.
 13. Theoptical information medium according to claim 11, comprising aninformation recording layer on the supporting substrate, alight-transmitting layer on the information recording layer, and thehard coat layer on the light-transmitting layer.